Selection of the Salt Tolerance Gene GmSALT3 During Six Decades of Soybean Breeding in China

Salt tolerance is an important trait that affects the growth and yield of plants growing in saline environments. The salt tolerance gene GmSALT3 was cloned from the Chinese soybean cultivar Tiefeng 8, and its variation evaluated in Chinese wild soybeans and landraces. However, the potential role of GmSALT3 in cultivation, and its genetic variation throughout the history of Chinese soybean breeding, remains unknown. Here we identified five haplotypes of GmSALT3 in 279 Chinese soybean landraces using a whole genome resequencing dataset. Additionally, we developed five PCR-based functional markers: three indels and two cleaved amplified polymorphic sequences (CAPS) markers. A total of 706 Chinese soybean cultivars (released 1956–2012), and 536 modern Chinese breeding lines, were genotyped with these markers. The Chinese landraces exhibited relatively high frequencies of the haplotypes H1, H4, and H5. H1 was the predominant haplotype in both the northern region (NR) and Huanghuai region (HHR), and H5 and H4 were the major haplotypes present within the southern region (SR). In the 706 cultivars, H1, H2, and H5 were the common haplotypes, while H3 and H4 were poorly represented. Historically, H1 gradually decreased in frequency in the NR but increased in the HHR; while the salt-sensitive haplotype, H2, increased in frequency in the NR during six decades of soybean breeding. In the 536 modern breeding lines, H2 has become the most common haplotype in the NR, while H1 has remained the highest frequency haplotype in the HHR, and H5 and H1 were highest in the SR. Frequency changes resulting in geographically favored haplotypes indicates that strong selection has occurred over six decades of soybean breeding. Our molecular markers could precisely identify salt tolerant (98.9%) and sensitive (100%) accessions and could accurately trace the salt tolerance gene in soybean pedigrees. Our study, therefore, not only identified effective molecular markers for use in soybean, but also demonstrated how these markers can distinguish GmSALT3 alleles in targeted breeding strategies for specific ecoregions.

Genome-Wide Investigation of Spliceosomal SM/LSM Genes in Wheat (Triticum aestivum L.) and Its Progenitors

The SSM/SLSM (spliceosomal Smith (SM)/SM-like (LSM)) genes are the central components of the spliceosome in eukaryotes, which play an important role in regulating RNA splicing, participating in diverse biological processes. Although it has been detected in Arabidopsis and rice etc. plants, the members and significance of the SSM/SLSM gene family in wheat are still not reported. In this study, we identified the SSM/SLSM genes in wheat and its progenitors at genome-scale, where 57 SSM/SLSM genes were identified in wheat, together with 41, 17and 19 found in Triticum dicoccoides, Triticum urartu, and Aegilops tauschii. Furthermore, their phylogenetic relationship, gene structures, conserved motifs, and cis-regulatory elements were systematically analyzed. By synteny analysis, good collinearity of SSM/SLSM genes was found among bread wheat and its progenitors’ genomes, and the distribution of SMD2 genes in wheat chromosome 5A, 4B and 4D located in the 4AL-5AL-7BS chromosome model, due to the translocation. Then, the positively selected genes were further investigated based on the non-synonymous to synonymous (dN/dS) analysis of the orthologous pairs. Finally, the expression profiles of the SSM/SLSM genes were detected using RNA-seq datasets, and eight stress-responsive candidate genes were selected to validate their expression through qPCR (real-time quantitative polymerase chain reaction). According to the co-expression network analysis, the correlation between the LSM7-7A gene and related genes was illustrated through Gene Ontology (GO) enrichment analysis. Furthermore, the LSM7-7A gene was related to the Arabidopsis homologous salt tolerance gene RCY1. This investigation systematically identified the complete candidates of SSM/SLSM genes and their characters in wheat and its progenitors, and provided clues to a better understanding of their contribution during the wheat polyploidy process.

Isolation of gene conferring salt tolerance from halophilic bacteria of Lunsu, Himachal Pradesh, India

Background Halophiles offer an attractive source of genes conferring salt tolerance. Halobacillus trueperi SS1 strain of Lunsu, Himachal Pradesh, India, a strict halophile, was exploited to isolate and clone the genes for salt tolerance. The genomic library of BamH1 digest of H. trueperi SS1 was constructed in pUC19, and recombinants were screened for salt tolerance on an LB medium containing ampicillin (100 μg/ml) and NaCl (0 to 1.5 M). Results One recombinant clone named as salt-tolerant clone (STC) conferred salt tolerance to host Escherichia coli/DH5α, which showed growth in the LB medium supplemented with ampicillin and 1.2 M NaCl. Restriction digestion and PCR analysis revealed the presence of an insert of approximately 2000 bp in the STC. DNA sequencing of the 2-kb insert on both strands yielded a sequence of 2301 nucleotides. Protein BLAST analysis of 2301-bp sequence of H. trueperi SS1 present in STC showed 97% identity to multidrug transport ATP binding/permease protein of Halobacillus karajensis. The insert contained in STC was subcloned into pGEX4T2 vector, and the recombinant clone STC/pGEX4T2 conferred salt tolerance to the bacterial host E. coli. Conclusions The present study led to the isolation of salt tolerance gene encoding a putative multidrug transport ATP binding/permease protein from H. trueperi SS1. The salt tolerance gene can be subcloned for transferring salt tolerance traits into agricultural crop plants for cultivation in saline and coastal lands.

Rice breeding on salt tolerance

Salt tolerance of rice is of great importance in agricultural production, since productivity of grain grown on saline lands largely depends on it. The paper deals with determining the presence of salt tolerance gene “Saltol” in rice hybrids obtained from crossing contrasting samples. To analyze salt tolerance, there were used seeds germinated in cups with distilled water and 1.5% NaCl solution, after which 10-day-old seedlings were weighed and their ratio to the control was determined. As a result of studies, there have been identified salt tolerant lines carrying the gene “Saltol” in a homozygous state. In the control nursery there were studied the best samples on productivity and elements of its structure. Two lines “7328” and “7322” were selected from the hybrid IR 52713-2B-8-2B-1-2 x Novator which significantly exceeded the standard variety “Yuzhanin” on 0.57-1.28 t/ha. On average for 2 years, they produced 6.82-7.53 t/ha (6.25 t/ha of the standard variety).

Assessment of salt tolerance and analysis of the salt tolerance gene Ncl in Indonesian soybean germplasm

Soybean [Glycine max (L.) Merr.] is one of the most important legume crops in the world. However, soybean grain yield is extensively affected by environmental stresses such as soil salinity. In this study, we evaluated the germplasm of 51 Indonesian soybean accessions for salt tolerance to identify salt-tolerant germplasms for possible use in breeding for soybean salt tolerance. Based on experiments under hydroponic conditions, adding 100 mM of NaCl to a 1/2 concentration of Hoagland and Arnon solution, several Indonesian soybean germplasms, such as Java 7, Seputih Raman, Tambora, Ringgit (JP 30217), Sinyonya (early) and Sinyonya (late) were identified as salt-tolerant in terms of salt tolerance rate (STR) and leaf chlorophyll content (SPAD value) taken with the Konica Minolta SPAD-502 chlorophyll meter. The selected salt-tolerant germplasms were further evaluated under soil medium cultivation in pots irrigated with 100 mM NaCl for around 5 weeks. The six selected soybean germplasms again showed higher salt tolerance in terms of SPAD, STR and shoot dry weight. Expression analysis of the salt tolerance gene Ncl revealed a significant positive correlation between Ncl expression and salt tolerance, suggesting that Ncl is essential for salt tolerance in the Indonesian soybean germplasms we tested. The salt-tolerant Indonesian soybean germplasms identified in this study could be used in local soybean breeding practices for the improvement of salt tolerance.

In Silico Design of PCR Primers to Amplify the Salt Tolerance Gene in Soybean

Soybean yield is decreased because of many stresses such as salt stress. Ionic and osmotic stresses are the effects of salt stress. An effective way of maintaining sustainable production in salt-affected soil is through breeding high salt tolerance soybean, which can be detected by PCR. The optimal PCR plays an important role in gene expression analysis. The success of a PCR-based method largely depends on the optimal primer sequence analysis in silico prior to a wet-bench experiment. Here we described designing of primer using web-based tools. Many types of online primer design software are available, which can be used free of charge to design desirable primers. The objective was to design of PCR primers to amplify the salt tolerance gene in soybean. A highly conserved region of 411 bases was detected by Clustal Omega. Primers were predicted using Primer3 based on conserved region, considering ideal conditions for primer length, hairpin, dimer, Tm, and GC%. The predicted forward and reverse primers were validated using NetPrimer. Both forward and reverse primers have shown significant similarity with salt tolerance gene and recommended to be used to amplify the salt tolerance gene in soybean.